This invention relates to a rotor of a dynamo-electric machine, and more particularly to means for preventing axial movement between a retaining ring and an end plate of a generator's rotor.
Many ways are known for securing a tubular sleeve to a cylindrical shaft. Some of these are designed to prevent relative rotation or transmit torque while others prevent relative axial movement. Keys, splines, pins and other similar retainers are generally used to secure elements such as gears or pulleys to shafts so that torque can be transferred between them or relative rotation prevented. Relative axial motion between a sleeve and a shaft is generally prevented by means such as a press or shrink fit between the parts, or set screws, pins, cotters or rings. All of these have distinct disadvantages for certain applications. For example, with very large parts heat-shrinking can require excessively high temperatures, especially in disassembling the sleeve from the shaft. Use of any type of pin typically requires a hole drilled or machined into the parts to be assembled. This can produce undesirably high stress concentrations under many operating conditions. The same disadvantage is suffered in the use of split rings or other retaining devices that typically require holes for assembly or disassembly tooling.
Desirable therefore is a device and method to interlock a sleeve with a shaft; a method which overcomes these disadvantages.
According to the invention a shaft is provided with a groove about its outer circumferential surface. A sleeve, having a central bore for receiving said shaft therethrough, has an eccentric groove about its inner circumferential surface. At least one detent is provided, said detent being an arcuate spring having an associated radius smaller than the radius of the shaft groove, a material thickness less than the depth of the shaft groove, and a height greater than the depth of the shaft groove. The detent is depressible during assembly and disassembly. The detent is positioned circumferentially about the shaft groove by spacers, so that its location can be positively identified for later disassembly.
During assembly the detent is positioned in, for example, the groove in the shaft. The sleeve is slid over the shaft, and over the positioned detent by depressing the detent into the shaft's groove. Once the sleeve is properly positioned over the detent, the detent's spring action resulting from its smaller radius causes the detent to spring into the sleeve's groove, straddling the interface between the shaft and the sleeve, and thereby preventing axial motion of the sleeve relative to the shaft.
During disassembly, with a four position eccentric groove as an example, the shaft is rotated 45 degrees relative to the sleeve. This positions the detent in radial alignment with a section of the eccentric groove in which the groove's depth is substantially zero. Thus, the rotation of the parts depresses the detent into the noneccentric groove and permits the sleeve and shaft to be slid apart.